| Mechanism of formation of the second haze and its controlling technology were studied in apple juice concentrate according to the practice of juice production .The main conclusions were made as followed:1. The contents of total phenolics, condensed tannins, soluble protein and metal iron such as K""\ Ca2\ Mg2+ in haze juice were higher than that in normal juice, but the contents of small phenolics were lower than that in normal juice.2. The turbidity of apple juice were reduced by freezing and increased by freezing and boiling. Globular particles of protein and chained particles of phenolic compounds negatively stained with uranyl acetate were observed through transmit electron microscope examination.They were the particles aggregated with each other or by themselves. The turbidity of post bottling haze was higher than that of the second haze in apple juice after 6 months storage.3. The main phenolic compounds in the second haze substances were polymers of procyanidin.Catechin and epicatechin were the precursors of formation of haze. The amino acids of protein in haze juice were hydrophobic and the contents of proline were higher in haze juice than that in normal juice.4. The turbidity were greater with two particular gelatin-tannic acid ratio(1:1 and 1:4w/w) than with other combination in pH3.7 buffer.The haze intensity of gliadin -catechin was greater in 25℃ than that in 80℃,and with the value of pH increasing in 2.5-4.2.The interaction between gliadin and catechin were hydrophobic bonding and hydrogen bonding. Starch leaded to retard haze in gliadin-catechin system while glucose, sucrose and pectin had no effects.5. The turbidity of haze and intensity of browning were increased in the chemical oxidative model system of catechin .epicatechin and chlorogenic acid at 50 ℃ in pH3.7 buffer. The main factors on the turbidity were kinds > temperature > value of pH .The oxidative products of catechin and epicatechin were the structure of o-quinone.The oxidative products was the mixtures of different molecular weight in catechin, epicatechin and chlorogenic acid model system. The interaction of haze products were hydrophobic bonding and hydrogen bonding. Haze produced was increased by KC1 and CaCl2.6. Intensity of browning was increased in the enzymic oxidation model system of catechin ,epicatechin and chlorogenic acid at 50℃ in pH3.7 buffer,but the turbidity of haze was increased few. The main factors on the browning degree were value of pH>kinds>temperature. The interaction of haze products were hydrophobic bonding and hydrogen bonding. Formation of haze was reduced by KC1 and CaCl2.7. Formation of haze in apple juice was reduced by enzymolysis, adsorption and ultralfiltration.The contents of catechin, epicatechin, chlorogenic acid, procyanidin 82 and condensed tannins were reduced by enzymolysis and adsorption. Ultra filtration process had no effects on the contents of catechin, epicatechin and chlorogenic acid, but reduced the contents of condensed tannins and soluble protein. The contents of soluble protein were decreased by adsorption, but were increased by enzymolysis.8. Addition of amylases and pectin enzyme retarded haze formation and reduced the contents of haze-active polyphenols with enzymolysis .Addition of PPO reduced the contents of haze-active polyphenols, but retarded formation of haze in moderate amount. The time of enzymolysis affected the adsorption process. The turbidity of haze was reduced in the moderate time of enzymolysis.The contents of haze-active phenolics was reduced by adsorption compared with enzymolysis alone. The turbidity of haze and contents of haze-active protein and haze-active phenolics were reduced if the surface area, distribution of micro-pores and the amount of active carbon were greater. The turbidity of haze and the contents of haze-active phenolics were reduced, but the contents of haze-active protein were increased by adsorption in high temperature.9. The turbidity of the second haze and contents of condensed tannin...
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